Guaranty

v. vouch for; give a guarantee; give a warranty; promise, assure

n. security; warranty; pledge; assurance

A surety is a person who agrees to be responsible for the debt or obligation of another. Additionally, the situation in which a surety is most typically required is when the ability of the primary obligor or to perform its obligations under a contract is in question, or when there is some public or private interest which requires protection from the consequences of the principal's default or delinquency. In most common law jurisdictions, a contract of suretyship is subject to the statute of frauds (or its equivalent local laws) and is only enforceable if memorialized by a writing signed by the surety.
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Noun
1. a collateral agreement to answer for the debt of another in case that person defaults
(synonym) guarantee
(hypernym) collateral

(n.)
In law and common usage: To undertake or engage that another person shall perform (what he has stipulated); to undertake to be answerable for (the debt or default of another); to engage to answer for the performance of (some promise or duty by another) in case of a failure by the latter to perform; to undertake to secure (something) to another, as in the case of a contingency. See Guarantee, v. t.
  

(n.)
In law and common usage: An undertaking to answer for the payment of some debt, or the performance of some contract or duty, of another, in case of the failure of such other to pay or perform; a guarantee; a warranty; a security.
  

One to whom a guaranty is made. This word is also used as a noun to denote the contract of guaranty or the obligation of a guarantor, and as a verb, to denote the action of assuming the responsibilities of a guarantor.